I assume you meant "in this proposal, the police could say". On first reading it looks like you meant that this was already possible today?

I don't know what country you think that is true in, but citation needed.

In the US at least, criminal convictions must be proven "beyond a reasonable doubt", they can't just say that they think there's information there, it must be proven that they already know it's there.

The hypothetical country the article writer wants to live in. The one where if you can't decrypt purported evidence of a crime you get the maximum sentence by default.